PlantLife Online

Answer

A small yield and large healthy plant is most likely caused by high levels of nitrogen in the soil or over fertilization.

For the best bean yield I recommend using a fertilizer formula with lower nitrogen like 5-10-10 incorporated into the garden soil prior to planting at a depth of around 6 inches. Once the bean plant has set flower and beans are beginning to develop you can side dress the crop with a higher nitrogen fertilizer if needed. The additional fertilizer may only be needed in climates with sandy, quick-draining soil and heavy rainfall. The same method should be used when growing most other beans in the garden including fava beans, green beans, pole beans, Lima beans and dry beans.